The Long-term Evolution-Advanced (LTE-A) heterogeneous network system includes a macro cell, a femto cell, a pico cell, an RRH and a relay. In which, the RRH has no signal processing capacity. Instead, the RRH forwards signals based on a base station, and transmits the signals of the base station indistinguishably in the form of radio wave with a transmitting power less than that of the base station.
FIG. 1 is a schematic diagram of the distribution of a base station and RRHs. As illustrated in FIG. 1, the base station is located at the center of a cell, and seven RRHs are provided in the coverage range of the base station, wherein the RRHs are uniformly distributed at edge positions of the cell, directly connected to the base station through optical cables and capable of forwarding signals transmitted by the base station. In conventional techniques, generally the base station determines a RRH used to serve the User Equipment (UE) according to the positions of the UE and the RRHs, and notifies the UE of an antenna to be measured. In such technique, since the antennas of the base station can be distributed on a plurality of RRHs, the number of antennas used by the base station and the number of antennas to be measured can be both reduced. When receiving signals from the base station and the RRH, or signals from a plurality of RRHs, the UE merges the received signals, which is corresponding to a macro diversity. By merging the signals, the signal strength at the client-side is enhanced and the system performance is improved.
But in the process of implementing the present invention, the inventor finds that the above technique has the following problem: when the UE is served by a plurality of devices (RRHs or base stations, hereinafter referred to as Service Equipments (SEs)), sometimes certain SEs have very low signal powers at the UE, and sometimes certain SEs have far lower signal powers than other SEs. The signals of the SEs of very low or far lower powers have no benefit in improving the reception performance of the UE, and even cause interferences and degrade the performance, while certain power shall be consumed when the RRH transmits the signals of the UE.
Meanwhile, when the UE is located at the edge of the RRH, in order to realize the selection of the RRH, the UE usually needs to measure the signal powers of respective RRHs. Sometimes the respective RRHs and the base station belong to the same cell, and the traditional mode that measures the Reference Signal Received Power (RSRP) based on Cell-specific Reference signal (CRS) cannot work under such scenario, thus a mode capable of distinguishing the respective RRHs is required to assist the base station to realize the selection of the RRH.
To be noted, the above introduction to the technical background is just made for the convenience of clearly and completely describing the technical solutions of the present invention, and to facilitate the understanding of a person skilled in the art. It shall not be deemed that the above technical solutions are known to a person skilled in the art just because they have been illustrated in the Background section of the present invention.